OK. No problem.
data task1;
format pt best12. ht best12. wt best12. colldate date9. sex $8.;
input pt ht wt colldate : date9. sex $8.;
cards;
1560401 155 70 22-Mar-06 Male
1560401 155 75 22-Jan-05 Male
1560402 150 60 03-Apr-05 Female
1560402 150 75 22-Jan-06 Female
1560403 165 70 22-Mar-06 Male
1560403 165 75 22-Jan-05 Male
1560404 150 60 03-Apr-05 Male
1560404 150 75 22-Jan-06 Male
1560405 145 50 22-Jan-06 Male
1560405 145 55 22-Jan-05 Male
1560406 150 80 03-Apr-05 Male
1560406 150 75 11-Apr-05 Male
1560407 165 70 15-Mar-06 Male
1560408 150 60 12-Dec-05 Female
1560408 150 75 22-Jan-06 Female
1560409 99 70 22-Oct-06 Male
1560409 99 75 22-May-05 Male
1560410 150 60 03-Dec-05 Male
1560410 150 105 22-Jan-06 Male
;
run;
proc sql;
select *,case when(count(*)=1) then 30
when(colldate=min(colldate)) then 10
when(colldate=max(colldate)) then 20
end as visit
from task1
group by pt;
quit;
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